Centrifugal compressor

ABSTRACT

The tendency towards instability of a centrifugal compressor with a rotor with fixed bent-forward vanes is decreased in providing in this rotor jet channels for supply of liquid which on rotation form liquid vanes. The direction of outflow of the jet openings are perpendicular to the axial direction of the rotor and the angle of outflow in respect to the radial direction are equal to the angle of the section of the fixed bent-forward vanes that is situated at the same diameter in the same plane of revolution.

[451 May 7, 1974 [5 CENTRIFUGAL COMPRESSOR 3,363,832 1/1968 Groff415/215 ux [75] Inventor: Peter Jacobus Collet, Voorschoten, FOREIGNPATENTS OR APPLICATIONS Netherlands 725,404 2/1932 France 415 116 [73]Assignee: Nederlandse Organisatie Voor t ToegepasbNatuurwetenschappelijkPrtmary ExammerCarlton R. Croyle onderzock Ten Behoeve van AssistantExaminer-Richard E. Gluck v Nijverheid, HandelvEn verkeer, The Attorney,Agent, or Firm-Watson, Cole, Grindle &

Hague, Netherlands Watson [22] Filed: I June 7, 1972 57 ABSTRACT [21Appl. No.: 260,662 7 The tendency towards instability of a centrifugalcompressor with a rotor with fixed bent-forward vanes is [30] F i A li ipriority Data' decreased in providing in this rotor jet channels for 7 7supply of liquid which on rotation form liquid vanes. Ju n e 2l, 1971Netherlands ....7108490 The direction of outflow of the j p g are 521U.S. c1. 417/78, 415/215 perpendicular to the axial direction of therotor and 51 11m. (:1. F04b 23/04, F04d 7/00- h angle of Outflow in P eto the radial direction 58 Field of Search 417/67, 78; 415/116, 215 areequal to the angle of the Section of the fixed 1 bent-forward vanes thatis situated at the same [56] References Cited diameter in the same planeof revolution.

UNITED STATES PATENTS 3 Claims, 3 Drawing Figures 3,630.641 12/1971 VanStaveren 417/67 I 3.481484 12/1969 Quinchon 417/78 X I 1,946,524 2/1934Crosthwait 417/78 X s 17 s 7 a BACKGROUND OF THE INVENTION The inventionrelates to a centrifugal compressor of 1 1 the type provided with adriven rotor with fixed vanes,

which are bent forward towards the periphery of the rotor and in itsdirection of rotation.

Such a centrifugal compressor is known in the art. Over a centrifugalcompressor with a rotor provided with radial vanes it has the advantagethat at equal circumferential velocity of the rotor the energytransferred per unity of weightof gas is higher. This advantagemanifests itself in a reduction of the speed or in a diminution of therotor-diameter for a centrifugal compressor, which hasto yield a desiredpressure ratio.

This advantage is faced by the disadvantage of an unfavorable adjustmentbehavior. For the energy transferred is far more dependent on thevolumetric flow of gas and namely such that a decrease in thisvolumetric flow of gas at constant speed causes a decrease in the energytransferred by the rotor per unit of weight of gas. The reduction in thepressure ratios attended with it, in general gives a still furtherreduction in thevolumetric flow of gas, causing a strong tendencytowards instability to arise. This form of instability-is indicated bythe term of surge in Anglo-Saxon literature.

The object of the present invention is to improve the adjustmentbehavior of the above centrifugal compressor by highly decreasing thetendency towards instability.

THE INVENTION The invention is characterized in that jets have beenprovided for the formation of fluid vanes in the rotor which jets on theone hand connect to a common central chamber linked up to an axial fluidsupply and on the other hand end in jet openings provided in asubstantially rotationally-symmetrical manner. The direction of outflowof these jetopenings are substantially perpendicular to the axialdirection of the rotor and the angle of outflow respecting the radialdirection being substantially equal to the angle of the section of thefixed bent-forward vanes that is situated at the same diameter in thesame plane ofrevolut'ion, and in that the rotor in the way known in theart is enclosed by a compression chamber for fluid vanes that is in openconnection with a fluid reservoir with which the fluid supply to thejets is connected and from which reservoir the compressed gas can bedischarged via an outlet.

The fluid vanes that at high speed emerge from the rotor contributeconsiderably towards the transfer of energy to the gas to be compressed.

At a constant speed the mass-flow of fluid, contrary to the mass-flow ofgas, is slightly affected by the gaseous pressure in thecompressor-outlet. Therefore, at a certain position of the control valvein the fluid supply duct, a reduction of the mass-flow of gas willresult in an increase in the mass-flow ratio between fluid and gas.

This causes an increase in the power that per unit of weight of gas istransferred to the gas via the fluid vanes. This increase compensatesthe decrease in the power transferred to the gas via the fixed vanes anda decrease in the pressure ratio that causes instability is avoided. I

The jets may have been provided in the rotor independent of the fixedbent-forward vanes.

Advantageously the jet openings are provided tips of the fixed vanes. i

Then, numerically, the jets correspond to the fixed bent-forward vanesand are partially provided in the fixed vanes. They can also be providedcompletely in the fixed vanes, thus in the center communicating with anannular common chamber in the way known in the art.

A further advantage is that the jets are completely provided in thefixed vanes.

DESCRIPTION OF THE DRAWING The invention will be further described withreference to the drawings showing by way of example a embodiment of theinvention, wherein FIG. 1 a vertical cross-section through a centrifugalcompressor, which is schematically shown;

FIG. 2 a section on an enlarged scale along line II-II of the rotor ofFIG. 3;

FIG. 3 a side-view on an enlarged scale of a part of the rotor.

The centrifugal compressor-shown in FIG. 1 consists of a compressorhousing 1, which is assembled with a fluid reservoir 2. A rotor 3 iscentrally mounted in compressorhousing l the rotor being which isfixedly connected to a shaft 4, with the bearing housing 5 thereoffixedly connected to housing 1.

Rotor 3 is driven by an electromotor 6 via shaft 4.

Rotor 3 is'provided with fixed vanes 7 that are bent forward at thegas-inlet side in the direction of rotation (see arrow in FIG. 3) and inrespect of the axial direction, and that serve for the compression ofgas, for example a freon gas, which is sucked by a suction nozzle 8.

Further, rotor 3, is provided with rotationallysymmetrical mounted jets9 abutting a central chamber 10, chamber 10 is connected to a fluidsupply duct 11 which, via an adjustment device 12, is connected to fluidreservoir 2.

The supply of fluid is effected as a result of the difference in gaseouspressure between the compressor-inlet and the compressor-outlet.

The chamber in which the fluid vanes are formed, is bounded by walls 13and 14 of compressor housing 1.

in the In a manner known in the art the compressed gas is separated fromthe fluid in fluid reservoir 2 with the aid of partitions l5 and thendischarged via outlet 16.

From the cross-section of a part of rotor 3 shown in FIG. 2, it can beclearly seen that via fluid supply 11 the.

fluid can enter into central chamber 10 and is further distributed overjets9.

Jet openings 17 are provided in the tips of fixed vanes 7, which areclearly illustrated in the side-view of a part of rotor 3 shown in FIG.3 on an enlarged scale.

Obviously, variations are made possible within the scope of theinvention. For example, in the event of a large number of fixedbent-forward vanes, these vanes may be alternately provided with a jet.The jet openings can also lie in a surface of revolution different fromthat of the tips of the vanes, provided the jet openings are situatedsuch that the fluid jets emerging from them are moving in a plane thatis radial in respect of the rotor-shaft.

I claim:

l. A centrifugal compressor, comprising:

a compression chamber having a central inlet for a a driven impellerdisposed generally in the center of said compression chamber;

i said impeller comprising a rotor provided with fixed vided in asubstantially rotationally-symmetrical manner, the direction of outflowof said outlet ends being substantially perpendicular to the axialdirection of said rotor, and the angle of outflow in respect of theradial direction being substantially equal to the angle of the sectionof the fixed bentforward vanes that is situated at the same diameter inthe same plane of revolution;

said compression chamber having a pair of spaced parallel walls disposedon opposite sides of said impeller and extending radially outwardly awayfrom said impeller and terminating in an annular fluid collectingchamber, said parallel walls forming a compression chamber for fluidvanes effecting a compressive action upon a gaseous medium therebetween;and

a fluid reservoir in open connection with said compression chamber andhaving a discharge pipe for the compressed gaseous medium.

2. A centrifugal compressor according to claim I, wherein the outletends of the jet channels are provided in the tips of the fixedbent-forward vanes.

3. A centrifugal compressor according to claim 2, wherein the jetchannels are completely provided in the fixed bent-forward vanes.

1. A centrifugal compressor, comprising: a compression chamber having acentral inlet for a gas; a driven impeller disposed generally in thecenter of said compression chamber; said impeller comprising a rotorprovided with fixed vanes which are bent forward towards the peripheryof the rotor in its direction of rotation; means for rotating saidimpeller; said rotor being provided with jet channels extendingtherethrough for the passage of a fluid, the inlet ends of Said jetchannels being connected to a central fluid chamber and the outlet endsbeing provided in a substantially rotationallysymmetrical manner, thedirection of outflow of said outlet ends being substantiallyperpendicular to the axial direction of said rotor, and the angle ofoutflow in respect of the radial direction being substantially equal tothe angle of the section of the fixed bent-forward vanes that issituated at the same diameter in the same plane of revolution; saidcompression chamber having a pair of spaced parallel walls disposed onopposite sides of said impeller and extending radially outwardly awayfrom said impeller and terminating in an annular fluid collectingchamber, said parallel walls forming a compression chamber for fluidvanes effecting a compressive action upon a gaseous medium therebetween;and a fluid reservoir in open connection with said compression chamberand having a discharge pipe for the compressed gaseous medium.
 2. Acentrifugal compressor according to claim 1, wherein the outlet ends ofthe jet channels are provided in the tips of the fixed bent-forwardvanes.
 3. A centrifugal compressor according to claim 2, wherein the jetchannels are completely provided in the fixed bent-forward vanes.